Utah DNR

In the West, the great outdoors is often just a few blocks away. Some of the most spectacular scenery is located in S.L.C., and Park City. But, occasionally you’d hear about what once was a hot spot for geodes. Never know, it may still b? e. ;-)
Next time your in Utah though, check out Dugway area, about 1−½ hours south of Tooele, give yourself a couple of days to explore the geode beds. Worth every minute or hour spent digging from near or far.
Geologic information: Approximately 6 to 8 million years ago (Miocene epoch), volcanic activity occurred in western Utah and deposited an extrusive igneous rock called rhyolite. Trapped gasses formed cavities within the rhyolite, and millions of years of ground-​water circulation allowed minerals to precipitate into the cavities. The result is geodes with spherical shapes and crystal-​lined cavities.
Roughly 32,000 to 14,000 thousand years ago, a large body of water known as Lake Bonneville covered most of western Utah. The lake’s wave activity eroded the geode-​bearing rhyolite and redeposited the geodes several miles away in the Dugway geode bed area as lake sediments.
Most geodes are typically hollow whereas others are completely filled with massive, banded quartz. The most common mineral found within the geodes is quartz in various colors: clear (rock crystal), purple (amethyst), and pink (rose).
Check out Utah Geological Website and let me know what you think!
P. S.s.s.s. I had the opportunity to give it a try several years ago, and dug up quite a bucket or two.
Happy digging